There are several Clamshell G3 iBooks (built in 1999/2000) in my family. Apart from changing the battery or keyboard, there was actually nothing wrong with the devices. Beginning with OS8, more current operating systems were used over time up to the Tiger, which of course required hard disk upgrades and memory upgrades.
In some clamshells I have also installed a DVD drive.
With limitations (the display only has a 800x600 resolution) you can still work well with them.
The housing has survived the years well with small scratches, there were the usual hairline cracks on the small Apple logo and the carrying handle. The fanless clamshells are quiet and don't get hot.